The Ecology of Forest Elephant Distribution and Its Implications for Conservation
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The Ecology of Forest Elephant Distribution and its Implications for Conservation Stephen Blake A thesis submitted for the degree of PhD University of Edinburgh 2002 PREFACE This thesis was written by myself and is the result of my own work, unless otherwise acknowledged at the end of appropriate chapters. ii ABSTRACT Genetic evidence suggests that extant African elephants, currently recognised as two sub-species in the genus Loxodonta, should be divided into distinct species; savannah elephants (L. africana) and forest elephants (L. cyclotis). Forest elephants are most abundant in the equatorial forest of the Congo Basin, and account for a considerable portion of Africa’s elephants. Despite their key role in forest ecosystems, few data on forest elephant ecology are available, at a time when intense hunting and widespread habitat fragmentation and conversion pose an increasingly severe extinction threat. A study of forest elephant ecology was initiated in the remote Ndoki Forest of northern Congo. The goal was to identify the ecological determinants of elephant distribution and ranging, and to determine the impact of human activity, at a relatively intact site. Data from a local, intensively surveyed site, and repeated extensive foot surveys over a 253km swathe of the Ndoki Forest, which traversed the northwest-southeast drainage gradient, revealed a spatial and temporal partitioning in the availability of resources important to elephants on several scales. Dicotyledon browse was most abundant in open canopy terra firma forest, light gaps, and swamps, while monocotyledon food was most concentrated in terra firma forest to the southeast, and was super-abundant in localised swamp patches. Mature and old leaf abundance was correlated with rainfall, but new leaves were not. During low rainfall periods, new leaf production was highest in the southeast, becoming widespread as rainfall increased. Forest clearings, clumped in the northwest, contained high mineral abundance in seep-hole water, most concentrated during dry periods. Fruit availability was negligible in swamps, high in closed canopy terra firma forest, and while correlated with rainfall, its temporal and spatial distribution was highly irregular. Drinking water, confined to rivers, was widespread and abundant. Elephants ate leaves, bark, wood, stems, roots, and fruit from over 350 plant species. Leaves dominated food selection, and browsing rates were highest in open canopy forests, particularly swamps. Fruit consumption increased dramatically as its availability increased. Elephants constructed trail systems that allowed efficient exploitation of high payback resources, notably water, minerals, and fruit. Elephant distribution and ranging was investigated using data from dung counts and GPS telemetry. Dung data showed that elephant abundance was consistently high in the northwest, most likely due to the influence of forest clearings and high quality swamp habitat, about which elephants were permanently aggregated. During dry periods, elephant abundance increased in the northwest and in proximity to rivers. As rainfall increased, elephants dispersed out of the northwest, they selected upland forest, and their distribution iii tracked the patchy distribution of fruit across the landscape. Telemetry data revealed that individual elephants ranged over large areas (up to nearly 2000km2), and travelled up to 57km in 48 hours, which allowed them to exploit resources over large areas. The widespread distribution of browse and drinking water, and the large body size of elephants, meant that quasi-nomadic ranging in search of fruit patches, was a low-risk strategy with a potentially high nutritional payback. The ecological determinants of elephant distribution and ranging were outweighed by human activity, including forestry prospection, and elephants avoided areas of high human impact. Their large-scale ranging patterns, and the widespread distribution of their resources, means that forest elephants are particularly vulnerable to habitat fragmentation. Road building to facilitate logging in remote forest blocks was identified as a major threat to the conservation of elephants. Immediate conservation actions were proposed, which include: the establishment and maintenance of large core areas of integrally protected habitat in remaining isolated forest blocks; planning for ecologically and socially optimal road construction; and reduced impact logging to conserve critical fruit trees. Applied research is required to identify potential conservation sites, improve survey methods, quantify the impact of logging on elephant ecology, ranging and demographics, and to understand the role of elephants in ecosystem function, and how it is disrupted by range restriction, population reduction, and logging. iv ACKNOWLEDGEMENTS It has been a privilege to study one of world’s most humbling animals, forest elephants, in one of its most enchanting environments, the equatorial forest of central Africa. I truly thank everyone who made this possible. My family has never failed to give me support and encouragement throughout my life. The stability and security they provide have helped me to freely pursue my interests, of which this thesis is one. I thank the Governments of Congo and CAR for permission to live and work in their countries. In particular, Mr. Henri Djombo, Minister of Forest Economy for Congo, Prof. Assori Itoua-Ngaporo of the Ministry of Scientific Research. Locally, the Conservator of the Nouabalé-Ndoki National Park, Mr. Yves Djoni-Bourgess, made the elephant study an integral part of park management. Two people shaped my life in the Ndoki Forest. Mike Fay introduced me to the forest and its elephants. Many of the ideas developed in this thesis originated from our early wanderings together deep in the Ndoki. In the early years at Ndoki, Richard Ruggiero created an environment in which my only responsibility was to explore and learn. I did not appreciate the extent of his contribution until years later. Many members of staff of the Nouabalé-Ndoki National Park (NNNP) worked hard toward the success of this project. The Director, Bryan Curran, mobilised aeroplanes, boats, trucks, money, and personnel, often at the last minute, to help this project run smoothly. I also thank Jerome Mokoko-Ikonga, Paul Elkan, Sarah Elkan, Dos-Santos Domingos, Mahammet Abdouyale, Richard Parnell, Mark Gately, Emma Stokes, Dave Morgan, Steve Gulick, and Gaston Gobolo. From The Dzanga-Sangha Project in CAR, I thank Allard Blom, Guy Rondou, Urbain Agatoua, Lisa Steel, Nigel Orbell, and especially Cloe Cipolletta. Staff of the logging company Congolaise Industrielle du Bois (CIB), particularly Mr. and Mrs. Glanaz, Michel Miller, and Fred and Mia Glanaz made the logging town of Pokola a holiday paradise after long stints in the forest. Heinrich Stol, CEO of the CIB, is thanked for his support. The timber-rich Goualougo Triangle, annexed to the National Park in 2001, was a huge contribution to elephant conservation on the part of Dr. Stol and the Government of Congo. Many people helped develop the research framework for this thesis. Mike Fay was instrumental. My Supervisor at Edinburgh University, Liz Rogers provided help, encouragement, and guidance to the end. Supervising probably her most infuriating P.hD. student coincided with the most difficult time of her life – sorry for that. Martyn Murray insisted that I should count leaves (in a forest!?), and Peter Jones made sure I was legal. The Research Co-ordinator of NNNP, Fiona Maisels, a local supervisor in Congo, v helped me to generate ideas, and tried to teach me to think logically. Dr. Maisels also helped to collect data from GPS telemetry collars. Collaboration with Peter Walsh expanded my original ideas, and has given ecological clarity and statistical validity to many of my observations. I learned a lot from discussions with Lee White and Andrea Turkalo. Dave Harris of the Royal Botanic Garden, Edinburgh, identified a large number of plants, often from appalling specimens. Gregoire Kossa-Kossa was counting trees in Congo before I started school, and it showed in his depth of knowledge. Clement Inkamba-Nkulu is perhaps the most conscientious person I have ever met. Patrick Boudjan worked hard and unselfishly. Peter, Gregoire, Clement, and Patrick played important roles in this thesis, and their contributions are acknowledged at the ends of appropriate Chapters. Billy Karesh and Sharon Deem, of the Field Veterinary Programme of WCS, provided expert medical supervision of elephant immobilisation, and, importantly, calm, quick minds under pressure. Both have my respect, and one has my love (sorry Billy). John Robinson and Kent Redford of WCS, and Jamie James of the Centre for Environmental Research and Conservation (CERC) at Columbia University gave me a place to write. Funding for this study was provided by the United States Fish and Wildlife Service, Save the Elephants, The Wildlife Conservation Society, The Global Environmental Facility (PROJECAP) and The Columbus Zoo. Without their generous support, this study could not have happened. All these organisations work hard for elephant conservation, and I hope they are happy with how their money was spent. Lotek Engineering Inc. (Toronto, Canada) generously loaned GPS telemetry hardware. Particular thanks go to Mark Phillips and Richard Ruggiero (USFWS), Beth Armstrong (Columbus), Amy Vedder (WCS), and John Vanden-Elzen and Leszek Meczarski (LOTEK). I have enjoyed an immensely rewarding collaboration